Enzyme-mediated film formation of melanin-like species from ortho-diphenols: Application to single-cell nanoencapsulation

Single-cell nanoencapsulation (SCNE) is a nanoarchitectonic strategy for creating cell-in-shell structures, in which the artificial shells, formed on individual living cells, protect the cells inside from otherwise lethal factors and also potentially provide them with advanced functions, such as exogenous biochemical reactions that are not attainable in wild-type cells. This work investigated enzymatic cascade systems for widening the substrate scope, beyond catecholamines, in the in-vitro formation of melanin-like films and shells and, ultimately, providing advanced building blocks and tools to the field of SCNE, inspired by the enzyme-derived structural diversification of melanin found in nature. The combination of glucose oxidase and horseradish peroxidase enabled the facilitated film formation of amine group-absent ortho-diphenols, such as protocatechuic aldehyde (PCA) and pyrocatechol. As a proof-of-demonstration, the developed reaction protocol was applied to the cytocompatible SCNE of Saccharomyces cerevisiae.